Transparent stdin / stdout

stdin.rb

class MyApp
  attr_accessor :input, :output

  def initialize
    @input  = $stdin
    @output = $stdout
  end

  def prompt_user 
    user_selection = gets.chomp              # => 'ponies'
    puts "User selected: #{user_selection}" # Displays User selected: ponies
    user_selection
  end

  def puts(*args)
    @output.puts(*args)    
  end

  def gets(*args)
    @output.gets(*args)
  end
end